Analyses of pollen and spores

A daily task of the aerobiologist during the pollen and spore season is to count airborne pollen and spores and to provide pollen reports and forecasts.

These information should guide people suffering from pollen and spore allergy to avoid those particles as far as possible.

How is the forecast made?

First of all the aerobiologist must know the current level of pollen and spores of different species in the air. Knowledge of the phenology of the plant species and the fungi included in the reports is essential. It is also of great importance to be aware of how far the flowering process of each species has proceeded.

The above mentioned steps have to be combined with the weather forecast, where wind directions, temperature, and precipitation play important roles. In other words, the pollen and spore forecast is a complicated process, where different parameters have to be considered.

How are airborne particels measured?

There are many ways in which the amount of airborne pollen and spores can be measured over a period of time. The method used at the Palynological laboratory is standardized in Europe and used widely abroad. In this method we use the Burkard Seven Day Recording Volumetric Spore trap.

​Burkard trap

The Burkard trap sucks a specific volume of air per unit of time (about 10 liters per minute) through a narrow, horizontal slit at the front. Behind the slit, inside the trap, a rotating drum is mounted.

A sticky tape covers the drum, so that particles carried with the air through the slit adhere to the tape. The drum rotates with a speed of two millimeters per hour, thus producing a sample of the particle content in the air at any given time.

Changing the drum

Every morning during the pollen season, the exposed drum is replaced by unexposed one. The exposed tape is removed from the drum and divided into 48 mm long Sections. Each section represents 24 hours of exposure. The sections are prepared for analysis by being embedded in mounting medium between a glass slide and a cover glass.

Analys

The glass slide is ready now for analysis with a light microscope at 400 x magnification. Pollen and spores of different species and taxa are counted separately in evenly spaced transverse sections across the tape.

A total of 12 such sections per day, each representing the mean value of 2 hours, are counted, after which the results of all the sections are added to get a daily mean. This will result in a specific figure for each of the species or taxa found on the tape, representing the amount of it's pollen or spores per cubic meter of air over the sampled 24-hour period.

​Forecast

The forecast is based on these data. Forecasts are distributed through many different channels, such as local radio stations, daily press, text-TV, TV and the Internet (in Swedish). Thereby, we hope, they will reach as many allergic as possible.